The present invention relates to an improved structure of triple-folding umbrella skeleton.
In FIGS. 2A, 2B, 2C, 3A, and 3B, two kinds of prior triple-folding umbrella skeletons are shown. FIG. 2A is a front elevational view of partial structure of one conventional triple-folding umbrella skeleton. FIG. 2B is an enlarged perspective view of the circular area marked "Z" in FIG. 2A. FIG. 2C is a side elevational view of the part shown in FIG. 2B. FIG. 3A is a front elevational view of partial structure of another conventional triple-folding umbrella skeleton. FIG. 3B shows that the umbrella skeleton of FIG. 3A is in a wholly open condition.
The conventional triple-folding umbrella skeleton, as shown in FIG. 2A, includes a hollow middle tube 7 and a plurality sets of frames mounted around the middle tube 7. For convenient illustrated, only one frame set is shown in FIG. 2A. Each frame set includes a first rib 1, a second rib 2, a third rib 3, a stretcher 4, and a link 5. A notch 71 is mounted at the upper portion of the middle tube 7. A runner 72 is slidably sleeved on the intermediate portion of the middle tube 7. An upper spring 73 is mounted in the middle tube 7, and has a part extending out of the surface of the middle tube 7 to lock the runner 72 at an upper position. One end of each first rib 1 is pivotably mounted on the runner 72, and the other end of the first rib 1 is pivotably mounted to one end of the second rib 2 via an eyelet 12. The other end of the second rib 2 is pivotably mounted to one end of the third rib 3 via an eyelet 23. One end of the stretcher 4 is pivotably mounted on the notch 71, and the other end of the stretcher 4 is pivotably mounted to the middle portion of the first rib 1. The second rib 2 further has an extension portion 20 longitudinally extending outwards from the eyelet 12. The link 5 is generally parallel to the first rib 1, and its two ends are pivotably mounted to the free end of the extension portion 20 and the stretcher 4 respecttively. FIG. 2B is an enlarged perspective view of the eyelet 23 (the circular area "Z" indicated in FIG. 2A). FIG. 2C is a side elevational view of the eyelet 23 shown in FIG. 2B. In FIG. 2C, the solid line of the third rib 3 indicates its position when the umbrella is opened, while the dotted line of the third rib 3 indicates its position when the umbrella is closed. When opening the above-described umbrella skeleton, a user must first pivot each third rib 3, along the direction of the arrow A, from the dotted-line position shown in FIG. 2C to the solid-line position of FIG. 2C about the eyelet 23, before pushing the runner 72 upwards to open all of the frame sets. If he does not pivot the third ribs 3 to the solid-line position in advance, the third ribs 3 may maintain at the dotted-line position when the umbrella is opened. In this case, the third ribs 3 cannot function at all. When a user wants to close the umbrella skeleton, he must first move the runner 72 downwards to the position shown in FIG. 2A until all of the frame sets are retracted to a generally closed condition, and then pivot each third rib 3, along the direction of the arrow B, from the solid-line position of FIG. 2C to the dotted-line position in order to wholly close the umbrella skeleton. Therefore, it is time-consuming and inconvenient to open or close the above conventional umbrella. Particularly, when the user is caught in a shower and has to open the umbrella immediately, it often happens that some of the third ribs 3 cannot be smoothly opened right away. Simimarly, it is also very difficult to completely close the umbrella by a single operation without arranging the canopy of the umbrella with hands in advance. Hence, the above prior triple-folding umbrella has many drawbacks.
In view of the above-described drawbacks, another structure of triple-folding umbrella skeleton as shown in FIGS. 3A and 3B is suggested. In comparison with the umbrella skeleton of FIG. 2A, the umbrella skeleton of FIG. 3A further includes a second link 6. The second link 6 is generally parallel to the second rib 2, and its two ends are pivotably mounted to the first rib 1 and the free end of an extension portion 30 of the third rib 3. In this case, the second link 6, the first rib 1, the second rib 2 and the third rib 3 are cooperated to form a second quadric link structure. When the runner 72 is moved upwards along the direction of the arrow C shown in FIG. 3A, the eyelet G' of the third rib 3 at which the second link 6 is pivotably mounted is moved upwards, resulting in the outer expansion of the third rib 3 along the direction of the arrow E. Therefore, the provision of the second link 6 can make the third rib 3 opened automatically when the runner 72 is moved upwards, so that the problems of the umbrella skeleton shown in FIGS. 2A-2C are solved.
However, the umbrella skeleton of FIG. 3A still suffers from some drawbacks. When each frame set is opened to a nearly wholly open condition as shown in FIG. 3B, that is, when the second link 6 is substantially aligned with the third rib 3, the eyelet G' is located between the eyelets F' and N'. The second quadric link structure formed by the second link 6, the first, second and third ribs 1, 2 and 3 is deformed into a triangle having three tips at the eyelets M', N' and F', respectively. Under such condition, since slight deformation of each frame set and, in particular, of each second rib 2 is necessary to permit the complete opening of the umbrella, and since the deformability of the members forming the triangle is quite limited, the user has to exert a relatively large force to overcome the deformation resistance by the frame sets during umbrella opening operation. In addition, it is found in practical use of this prior triple-folding umbrella that, when the parallelogram M'P'Q'R' is being moved as the umbrella is being opened, its movement is greatly restrained by the nearly rigid second link 6 which is pivotably mounted at the point N' of the first rib 1. It is found in real operation that the sizes of the ribs and link forming the parallelogram M'P'Q'R' cannot be too small, or the expansion of the third rib 3 will be very difficult.